The present invention relates generally to beverage dispensing equipment, and in particular to beverage or syrup sold out sensing systems therefor.
Beverages are dispensed generally either in a pre-mix form, wherein plain or carbonated water and syrup have been previously combined in the desired ratio to form a finished drink, or in a post-mix form wherein the water and syrup are combined in an on-demand basis at the point of dispense. The pre-mix drink, or the syrup in the case of post-mix, can be retained in, for example, a stainless steel tank or bag-in-box container. The container can then be fluidly connected to a dispenser for the delivery of the drink or syrup thereto. A continuing problem involves sensing when the reservoir of beverage or syrup is empty so that an appropriate sold-out signal can be generated indicating that the empty container should be changed out for a new one.
One existing system looks at the current demand of the solenoid of the dispensing valve of such dispensers. If the current demand is high, i.e. the solenoid is opening against a pressure force, then it is interpreted that there is sufficient beverage. If the current draw is low, then that indicates that the valve is encountering no resistance to open, which is interpreted as no beverage being present. This system works well but is limited to solenoid operated valves. Other systems use fluid conductivity sensors to sense the presence of beverage or syrup as it flows through a delivery line to the dispense valve. However, such an approach presents problems with respect to cleaning the sensors to insure that they work properly. Also, such sensors must be sanitized when changing out to a new container of beverage or syrup. Sensors are also known to determine the fluid level in a container with the use of reflection of a light signal, such as infrared, or to determine volume by weight change in weight of the container as it empties. While such sensing approaches will work, they also can present sanitation concerns as well as reliability and accuracy problems.
Accordingly, it would be desirable to have a sold-out sensing system that is reliable, accurate and that does not contact the fluid being sensed.
The present invention is a sold out system and method for use with any container of liquid or the like that is emptied by use of a pump. The pump can be of any electric motor driven variety such as, peristaltic, diaphragm, or piston. A microprocessor based control circuit includes a current sensing circuit for determining a voltage value which correlates proportionally with the current demand of the motor driving the pump. If the sensed voltage is high, that indicates the pump is encountering resistance and fluid is present. Conversely, if the sensed voltage use is low, that is taken to indicate that the pump is not pumping any liquid and that the container is empty.
In particular, the control senses an actual sold out condition in one of two ways. First, if the control senses a large variation between voltage samplings during a dispense cycle, that is taken to indicate a situation where the syrup or beverage is running out, i.e. the pump is moving a non-continuous stream of product. It can be very useful to signal a sold out condition before all of the beverage is dispensed from the container, as a discontinuous stream can result in an undesirable xe2x80x9csputteringxe2x80x9d performance, and can throw off the proper ratio in the case of a post-mix dispensing. Secondly, if there is no significant difference between the sensed voltages, but the sensed voltage is significantly below the reference voltage that would be expected if fluid were present, that situation indicates that the reservoir of product is totally empty. Thus, for example, where a fairly continuous dispense has occurred to the point where essentially all the beverage has been removed from the container, such a sold out condition must also be sensed and indicated.
An important aspect of the present invention is to monitor the voltage levels during dispensing and to adjust for changes in the reference voltage value that can occur over time. It was found that the initial reference value would become inaccurate over time or with changes in ambient conditions. For example, it was found that a new pump, and especially one with a gear case, would demand more current to be operated when new than after it had been used and xe2x80x9cbroken-inxe2x80x9d. Thus, as the pump becomes easier to operate the voltage difference between the initially programmed high value and a sold out value decreases over time, i.e. there is a downward drift in the voltage requirement of the motor independent of the liquid being pumped. Changes in many other values, such as, the tubing employed through which the liquid is pumped, or ambient temperature could affect the effort needed to pump the liquid. In the case of temperature, the fluid could become more or less viscous thereby increasing or decreasing, respectively, the voltage requirements. As a result thereof, an actual sold out condition may not be sensed or in the reverse, a sold out condition could be indicated where none exists.
The present invention uses a software routine to sense the average current requirements during dispensing and adjust the reference voltage for the normal full reservoir pump current value based on a historical average thereof as indicated by a predetermined number of prior dispense cycles. The control uses the adjusted reference voltage as a base for determining a sold out condition. Thus, the control of the present invention has the ability to xe2x80x9clearnxe2x80x9d over time and to compensate for physical changes in hardware and in the environment to provide for accurate sold-out determinations.